PI: Muhannad Suleiman
Co-PI(s): Clay Naito
University: Lehigh University
Industry partner: Clean Air Council
The use of renewable offshore wind energy in the U.S. has been growing rapidly and is expected to become an industry that is worth more than $1 trillion within the next two decades. Offshore wind turbines (OWTs) are conventionally supported on large-diameter, smooth-surface, steel foundations (piles or suction caissons) with the foundations contributing ~14% to 34% of the whole OWT project cost (Stehly 2020 and Bhattacharya 2019). Currently, the U.S. does not have the capability to fabricate large-diameter, steel foundations and instead relies on foundations fabricated abroad. Our team proposes to develop an innovative foundation system fabricated from Ultra High-Performance Concrete (UHPC). Unlike high-cost foreign steel systems, the UHPC foundation can be produced domestically and produced pre-cast, pre-stressed, concrete products which have well-established regional partners with members of the team. Additionally, this proposal uses an existing, reliable, and scalable UHPC material as an alternative to conventional steel to enhance domestic supply chains and reduce dependency on foreign manufactured foundations. With the industry trends of using larger size turbines and harvesting energy at locations with deeper water, higher loads are expected and the use of multiple foundations to support OWTs are becoming more common. Applied loads are predominantly transferred through long-term cyclic axial loading (compression-tension). Soil-foundation interaction (SFI) under these demands are the most unfavorable due to accumulated vertical displacement, which increases with the number of cycles and load amplitude. Furthermore, current design methods using large-diameter, steel foundations with smooth surfaces require conservative designs due to friction fatigue. Therefore, we propose investigating bio-inspired optimized surfaces of foundations to maximize anisotropic friction for improving the axial pull-out resistance and decreasing the accumulated upward displacement while having lower friction between the foundation and surrounding soil during installation.